Program Director/Principal Investigator (Last, First, Middle): Herring, Bruce, E. PROJECT SUMMARY Autism Spectrum Disorder (ASD) is a leading cause of mental impairment for which there is no known cure. Mounting evidence points to a convergence on altered actin-mediated regulation of postsynaptic glutamatergic synaptic function as a basis for ASD. We have recently identified an unprecedented clustering of ASD-related mutations in the GEF1 domain of the synaptic actin regulatory protein, Trio, that results in a strong genome-wide statistical association of the TRIO gene with ASD. The long-term goal of our research is to identify core synaptic regulatory machinery onto which numerous ASD causing factors converge. Identification of synaptic ?convergence points? of ASD-risk genes will help simplify the genetic landscape of this disorder and thus, aid in the development of new strategies to treat individuals with a diverse array of ASD-causing factors. Our central hypothesis is that ASD mutations in Trio disrupt a multitude of synaptic regulatory pathways, and that disruption of these pathways results in glutamatergic synapse dysfunction that contributes to the development of ASD- related behavioral phenotypes. Guided by strong preliminary data we will pursue this hypothesis in three specific aims. In Aim 1, we will combine proteomic, biochemical, electrophysiological, and super-resolution imaging techniques to identify novel synaptic regulatory mechanisms involving Trio. In Aim 2, we will combine these same approaches with computational modeling to reveal Trio-related synaptic regulatory mechanisms disrupted by Autism-related mutations and provide a comprehensive picture of the synaptic disruption that results from Autism-specific Trio dysfunction. And, for Aim 3, we have engineered a conditional knock-in mouse that allows CRE-dependent expression of an ASD-related mutant form of Trio. Using this new and powerful genetic tool, we will conduct a battery of behavioral tests to assess the impact of ASD-related Trio mutations on mammalian behavior. Growing evidence now suggests that neurological sensory processing deficits underlie the development of many common ASD-related behavioral phenotypes. Because of this, we propose the use of state-of-the-art techniques that allow careful examination of somatosensory processing in these mice. The present proposal is innovative because it assembles a team of collaborators with diverse areas of expertise and deploys new and powerful genetic tools that will allow a multi-dimensional approach to understanding how disruption of synaptic function leads to ASD. The proposal is significant because it stands to identify an important synaptic signaling hub that links numerous synaptic proteins previously implicated in ASD and will vertically advance our understanding of ASD from synapse to circuit to behavior. This proposal squarely meets the mission objectives of the NINDS given its focus on how synaptic dysfunction ultimately leads to key neurological deficits that likely underlie many core behavioral phenotypes associated with ASD. OMB No. 0925-0001/0002 (Rev. 01/18 Approved Through 03/31/2020) Continuation Format Page